Irene Gallego

Farm Ponds as Potential Complementary Habitats to Natural Wetlands in a Mediterranean Region

We compared morphometric and physico-chemical characteristics of farm ponds and natural wetlands in Andalusia (southern Spain) to determine whether artificial waterbodies might act as alternative and/or complementary habitats for aquatic biodiversity. Farm ponds were much smaller than natural wetlands, making them unsuitable for species requiring large waterbodies. However, we observed high farm pond density in areas lacking natural wetlands, which suggests a prime role for the conservation of species with low dispersal capacities. Natural-substrate ponds were abundant in traditional extensive farming systems and showed shoreline complexity as high as the most complex natural wetlands. Areas with more intensive agriculture were dominated by artificial-substrate ponds and wetlands, with low physical complexity in both. The high copper load in sediments, due to the use of copper sulphate as biocide, differentiated the artificial-substrate ponds from natural-looking ponds and all natural wetland types. Aqueous mineral levels in farm ponds were much lower than in natural wetlands. We can conclude that farm ponds might play a principal role in region-wide habitat complementarity, by providing a relatively high density of small, permanent, oligohaline waterbodies that is not matched by natural wetland. To enhance this role, measures regulating both pond construction and management are needed, particularly for artificial-substrate ponds.

Pond management and water quality for drip irrigation in Mediterranean intensive horticultural systems

The influence of pond management on water quality for drip-irrigated crops was studied throughout a field survey and a mesocosm experiment. Water sources were pooled into two groups: ground or surface water (GW/SW) and recycled wastewater. Pond covering, which was limited to about a quarter of them, improved water quality by reducing phytoplankton biomass. However, biocide applications and pond dredging were ineffective at improving in-pond water quality. Dredging did not reduce the concentrations of planktonic chlorophyll a or total suspended solids (TSS) in GW/SW fed ponds, whereas biocide applications increased both parameters. Field and experimental data proved that the two predominant taxa of submerged aquatic vegetation (SAV) found in ponds (Potamogeton pectinatus and Chara spp.) improved water quality by increasing water oxygenation and decreasing chlorophyll a and TSS concentrations. Preserving SAV (especially Chara spp.) appears to be an environment-friendly, cost-effective and recommendable alternative strategy for irrigation pond management.

Physical, chemical, and management-related drivers of submerged macrophyte occurrence in Mediterranean farm ponds

The construction of ponds for irrigation has proliferated during last decades in Mediterranean regions. If properly constructed and managed, ponds may simultaneously meet conservation and agricultural objectives: the preservation of certain macrophytes might improve water quality for irrigation purposes. However, the effects of management are often neglected when analyzing the main drivers of organisms community structure. Here we investigated the effect of environmental variables, construction type and management practices on the occurrence of submerged macrophytes (vascular plants, charophytes, filamentous algae). Total submerged macrophyte coverage and richness did not vary with pond type, but the presence of submerged macrophytes was significantly higher in embankment ponds. Artificial ponds showed the highest charophyte richness but lowest vascular plant occurrence. Total submerged macrophyte occurrence mainly correlated with conductivity and littoral vegetation, whilst the relative importance of environmental factors was higher than variables related to pond type and management. However, embankment ponds showed the highest richness of vascular plants and filamentous algae, and artificial ponds contributed to the regional pool of charophyte species. Thus, construction pond type and management levels might be relevant to understand submerged macrophytes occurrence in man-made ponds, since the three pond types contributed to the local and regional species pool.

Management effects on fungal assemblages in irrigation ponds: are biodiversity conservation and the control of phytopathogens compatible?

The study of fungi and fungus-like organisms in irrigation ponds has applied interest since waterborne phytopathogens can disperse through the irrigation system to the crop roots. We tested the hypothesis that manag- ing irrigation ponds to maintain high levels of biodiversity could entail agronomic benefits through the control of phytopathogens. The structure of assemblages of fungi and fungus-like taxa were characterized and compared us- ing samples taken from two strata depths (superficial and deep). This was done in four management/water source pond groups of southeastern Spain: groundwater-fed ponds with submerged aquatic vegetation stands (untreated SAV ponds); groundwater-fed ponds submitted to low and high doses of copper sulfate, and ponds fed with recy- cled urban wastewater bearing intermediate doses of copper sulfate. Higher density and diversity of fungi, besides a singular assemblage composition, were found in untreated SAV ponds compared to treated ponds, particularly for samples taken in the deep stratum. Phytopathogenicity of the main phytopathogens detected (Pythium isolates) was generally low and rather unaffected by the type of pond management. However, much evidence from poten- tial unsuitable hosts (submerged macrophyte species) and fungal composition (related to the presence of potential pathogen antagonists) suggests that managing ponds to preserve submerged vegetation might prove useful for controlling root rot diseases.